Drugs Used in Cardiac Arrhythmias Flashcards
What cardiac structures are involved with the fast action potential?
1) Ventricular cardiomyocytes
2) Atrial cardiomyocytes
3) Purkinje fibers
What cardiac structures are involved with the slow (pacemaker) action potential?
1) SA node cells
2) AV node cells
What occurs during phase 0 of the fast action potential?
During phase 1?
Phase 2?
Phase 3?
Phase 4?
0) Na+ channels open due to depolarization and Na+ enters the cells
1) K+ exits cells
2) Plateau phase results from K+ exiting cells offset by and Ca2+ entering
3) Ca2+ channels close and K+ begins to exit more rapidly resulting in repolarization
4) Resting membrane potential is gradually restored by Na+/K+ ATPase and the Na+/Ca2+ exchanger
What occurs during phase 4 of the slow (pacemaker) action potential?
During phase 0?
Phase 3?
4) Slow spontaneous depolarization via T-type Ca2+ channels
0) Upstroke of Action Potential via L-type Ca2+ channels
3) Repolarization by inactivation of calcium channels with increased K+ efflux
What are the functions of the class 1A drugs?
1) Block sodium channels
2) Block potassium channels
What are the class 1A drugs?
1) Quinidine
2) Procainamide
3) Disopyramide
Procainamide has what effect on the SA and AV nodes?
What is its clinical use?
What adverse effect is noted with it?
1) Depresses their activity
2) Sustained ventricular tachycardias and arrhythmias associated with MI
3) Lupus related side effects
Both Quinidine and disopyramide have what effect on the heart?
What is the clinical use of disopyramide?
1) Antimuscarinic effect
2) Recurrent ventricular arrhythmias
What adverse effect is seen with the class 1A drugs?
QT interval prolongation and induction of torsade de pointes arrhythmia and syncope
What is the function of the class 1B drugs?
Block sodium channels
Why do class 1B drugs not prolong action potential or QT duration on ECG like class 1A drugs do?
They do not block potassium channels
What are the class 1B drugs?
1) Lidocaine
2) Mexiletine
What is the clinical use of lidocaine?
What is the route of administration?
1) Stop ventricular tachycardia from acute MI
2) IV
What is the clinical use of Mexiletine?
What is the route of administration?
1) Ventricular arrhythmias
2) Oral
What are the functions of the class 1C drugs?
1) Block sodium channels
2) Block certain potassium channels
What are the class 1C drugs?
1) Flecainide
2) Propafenone
What are the clinical uses of flecainide?
1) In patients with normal hearts who have supraventricular arrhythmias
2) Refractory ventricular arrhythmias that are life threatening
What are the clinical uses of propafenone?
How is its effect on beta-blocking?
1) Supraventricular arrhythmias in patients without structural disease
2) Weak
What adverse effect is seen with the class 1C drugs?
Exacerbation of ventricular arrhythmias
Beta-Blockers (Class 2 drugs) have what effect on the pacemaker action potential?
1) Increased slope due to effects on If (funny current) and T-type Ca channels
2) Reduced threshold potential due to effect on L-type Ca channels
Beta blockers have what effect on the SA node?
On the AV node?
1) Decrease HR and increase RR interval
2) Decrease AV conduction and increase PR interval
What are the beta blockers used to Tx arrhythmias?
1) Propranolol
2) Esmolol
What type of beta blocker is esmolol?
Short acting selective beta-1 blocker
Which beta blocker is used as a continuous i.v. infusion, with rapid onset
and termination of its action?
Esmolol
What are the actions of the class 3 drugs?
1) Block potassium channels
2) Prolong QT interval
What are the class 3 drugs?
1) Amiodarone
2) Sotalol
3) Dofetilide
4) Ibutilide
Besides blocking potassium channels what else does Amiodarone do?
What is its clinical use?
1) Blocks inactivated Na2+ channels and calcium channels
2) Recurrent ventricular tachycardia and atrial fibrillation
What potentially fatal adverse effect is associated with amiodarone?
Pulmonary fibrosis
Besides blocking potassium channels what else does Sotalol do?
What is its clinical use?
1) Non-selective beta blocker
2) Treatment of life-threatening ventricular arrhythmias
What adverse effect is seen with sotalol?
Provokes torsade de pointes
What do dofetilide and ibutilide specifically block?
What is its clinical use?
1) Rapid component of the delayed rectifier potassium current
2) Restore sinus rhythm in patients with atrial fibrillation
What adverse effect is seen with dofetilide and ibutilide?
QT interval prolongation and increased risk of ventricular arrhythmias
What are the actions of the class 4 drugs?
It is active in cells exhibiting what type of potential?
1) Block L-type Calcium channels
2) Pacemaker potential
What effect do the class 4 drugs have on the pacemaker potential?
1) Decrease the slope of phase 0 depolarization
2) Increase L-type Ca2+ channel threshold potential
What are the class 4 drugs?
1) Verapamil
2) Diltiazem
What is the clinical use of verapamil and diltiazem?
Termination and prevention of paroxysmal supraventricular tachycardia
Adenosine activates A1 adenosine receptor which is a?
It has what effect on ions?
What effect does it have on the AV node?
1) Gi coupled GPCR
2) Enhances potassium current and inhibits Ca2+ and Funny currents
3) Inhibits AV conduction and increases AV nodal refractory period
What is the clinical use of adenosine?
Conversion to sinus rhythm in paroxysmal supraventricular tachycardia
What is proarrhythmia?
Drug-induced significant new arrhythmia or worsening of an existing arrhythmia
Which classes of drugs cause excessive slowing of repolarization which leads to torsades de pointes?
Which causes excessive slowing of conduction leading to persistent ventricular tachycardias?
1) Class 1A and Class 3 drugs
2) Class 1A and 1C drugs
Atrial fibrillation is initiated and sustained due to formation of?
Reentry circuits
Reentry is a type of arrhythmia in which?
One impulse re-enters and excites areas of the heart more than once
What is the atrial activation rate in atrial fibrillation?
The ventricular rate?
1) 350-600 bpm
2) 120-180 bpm
What is used to treat Afib?
Direct current cardioversion
What drugs are used as chemical cardioversion in the treatment of Afib?
1) Class 1C agents
2) Class 3 agents
How do class 1C agents terminate reentry in order to treat Afib?
Class 3 agents?
1) Block fast Na+ channel to reduce retrograde conduction through damaged tissue
2) Block K+ channels to keep cells in their refractory period
What drugs are used in order to maintain sinus rhythm in AFib patients with structural heart disease?
The Class 3 drugs:
1) Sotalol
2) Amiodarone
3) Dofetilide
(Class 1C drugs are contraindicated in this case)
What is the most common type of paroxysmal supraventricular tachycardia?
Atrioventricular nodal reentrant tachycardia
What does paroxysmal supraventricular tachycardia look like on ECG?
1) Narrow QRS
2) Tachycardia
3) P wave inverted or hidden in QRS
What drugs are used in the prevention of paroxysmal supraventricular tachycardia?
Class 4 drugs:
1) Verapamil and Diltiazem
Class 2 drugs:
2) Metoprolol and propranolol
Torsade de pointes is often associated with impaired function of?
This leads to?
1) Potassium channels
2) Prolonged repolarization
Torsade de pointes is associated with what syndrome?
Long QT syndrome
What drugs can cause the form of Torsade de pointes known as acquired long QT syndrome?
1) Class 1A
2) Class 3 (Amiodarone excluded)
